Java Tutorial/Apache Common/HashCodeBuilder

Custom HashCode Builder

/* 
 * ========================================================================
 * 
 * Copyright 2005 Tim O"Brien.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *   http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * 
 * ========================================================================
 */
import java.math.BigDecimal;
import java.util.HashSet;
import java.util.Set;
import org.apache.rumons.lang.builder.rupareToBuilder;
import org.apache.rumons.lang.builder.EqualsBuilder;
import org.apache.rumons.lang.builder.HashCodeBuilder;
import org.apache.rumons.lang.builder.ToStringBuilder;
class TaxReturn {
  private String ssn;
  private int year;
  private String lastName;
  private BigDecimal taxableIncome;
  public TaxReturn() {
  }
  public TaxReturn(String pSsn, int pYear, String pLastName, BigDecimal pTaxableIncome) {
    setSsn(pSsn);
    setYear(pYear);
    setLastName(pLastName);
    setTaxableIncome(pTaxableIncome);
  }
  public String getSsn() {
    return ssn;
  }
  public void setSsn(String pSsn) {
    ssn = pSsn;
  }
  public int getYear() {
    return year;
  }
  public void setYear(int pYear) {
    year = pYear;
  }
  public String getLastName() {
    return lastName;
  }
  public void setLastName(String pLastName) {
    lastName = pLastName;
  }
  public BigDecimal getTaxableIncome() {
    return taxableIncome;
  }
  public void setTaxableIncome(BigDecimal pTaxableIncome) {
    taxableIncome = pTaxableIncome;
  }
  public String toString() {
    return new ToStringBuilder(this).append("ssn", ssn).append("year", year).append("lastName",
        lastName).toString();
  }
  public int hashCode() {
    return new HashCodeBuilder(3, 7).append(ssn).append(year).toHashCode();
  }
  public boolean equals(Object pObject) {
    boolean equals = false;
    if (pObject instanceof TaxReturn) {
      TaxReturn bean = (TaxReturn) pObject;
      equals = (new EqualsBuilder().append(ssn, bean.ssn).append(year, bean.year)).isEquals();
    }
    return equals;
  }
  public int compareTo(Object pObject) {
    return CompareToBuilder.reflectionCompare(this, pObject);
  }
}
public class MainClass {
  public static void main(String[] pArgs) throws Exception {
     TaxReturn return1 = new TaxReturn("012-68-3242", 1998, "O"Brien", new BigDecimal(43000.00));
     TaxReturn return2 = new TaxReturn("012-68-3242", 1999, "O"Brien", new BigDecimal(45000.00));
     TaxReturn return3 = new TaxReturn("012-68-3242", 1999, "O"Brien", new BigDecimal(53222.00));
     System.out.println("HashCodeBuilder: " + return2.hashCode());
     Set set = new HashSet();
     set.add(return1);
     set.add(return2);
     set.add(return3);
     System.out.println(set);
  }
}

HashCodeBuilder: 219210998
[TaxReturn@7ffe01[ssn=012-68-3242,year=1998,lastName=O"Brien], TaxReturn@471e30[ssn=012-68-3242,year=1999,lastName=O"Brien]]

HashCode Builder

/* 
 * ========================================================================
 * 
 * Copyright 2005 Tim O"Brien.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *   http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * 
 * ========================================================================
 */
import org.apache.rumons.lang.builder.rupareToBuilder;
import org.apache.rumons.lang.builder.EqualsBuilder;
import org.apache.rumons.lang.builder.HashCodeBuilder;
import org.apache.rumons.lang.builder.ReflectionToStringBuilder;
class BuilderBean implements Comparable {
  private String prop1;
  private String prop2;
  public String getProp1() {
    return prop1;
  }
  public void setProp1(String pProp1) {
    prop1 = pProp1;
  }
  public String getProp2() {
    return prop2;
  }
  public void setProp2(String pProp2) {
    prop2 = pProp2;
  }
  public String toString() {
    return ReflectionToStringBuilder.toString(this);
  }
  public boolean equals(Object pObject) {
    return EqualsBuilder.reflectionEquals(this, pObject);
  }
  public int compareTo(Object pObject) {
    return CompareToBuilder.reflectionCompare(this, pObject);
  }
  public int hashCode() {
    return HashCodeBuilder.reflectionHashCode(this);
  }
}
public class MainClass {
  public static void main(String[] pArgs) throws Exception {
    // Builder and Builder2 contain the same content
    BuilderBean builder = new BuilderBean();
    builder.setProp1("One");
    builder.setProp2("Two");
    BuilderBean builder2 = new BuilderBean();
    builder2.setProp1("One");
    builder2.setProp2("Two");
    BuilderBean builder3 = new BuilderBean();
    builder3.setProp1("Uno");
    builder3.setProp2("Dos");
    System.out.println("HashCodeBuilder: " + builder.hashCode());
  }
}

HashCodeBuilder: 3046707

HashCodeBuilder.reflectionHashCode

import org.apache.rumons.lang.builder.EqualsBuilder;
import org.apache.rumons.lang.builder.HashCodeBuilder;
import org.apache.rumons.lang.builder.ToStringBuilder;
import org.apache.rumons.lang.builder.ToStringStyle;
public class MainClass {
    public static void main(String[] args) {
        MyClass one = new MyClass("Becker", 35);
        MyClass two = new MyClass("Becker", 35);
        MyClass three = new MyClass("Agassi", 33);
        System.out.println("One>>>" + one);
        System.out.println("Two>>>" + two);
        System.out.println("Three>>>" + three);
        System.out.println("one equals two? " + one.equals(two));
        System.out.println("one equals three? " + one.equals(three));
        System.out.println("One HashCode>>> " + one.hashCode());
        System.out.println("Two HashCode>>> " + two.hashCode());
        System.out.println("Three HashCode>>> " + three.hashCode());
    }
}
class MyClass {
    private String name = null;
    private int age = 0;
    public MyClass(String name, int age) {
        this.name = name;
        this.age = age;
    }
    public boolean equals(Object obj) {
        return EqualsBuilder.reflectionEquals(this, obj);
    }
    public String toString() {
        return ToStringBuilder.reflectionToString(this,
            ToStringStyle.MULTI_LINE_STYLE);
    }
    public int hashCode() {
        return HashCodeBuilder.reflectionHashCode(this);
    }
}

One>>>MyClass@743399[
  name=Becker
  age=35
]
Two>>>MyClass@1d8957f[
  name=Becker
  age=35
]
Three>>>MyClass@3ee284[
  name=Agassi
  age=33
]
one equals two? true
one equals three? false
One HashCode>>> 462213092
Two HashCode>>> 462213092
Three HashCode>>> -530629296

HashCode For String

import org.apache.rumons.lang.builder.EqualsBuilder;
import org.apache.rumons.lang.builder.HashCodeBuilder;
import org.apache.rumons.lang.builder.ToStringBuilder;
import org.apache.rumons.lang.builder.ToStringStyle;

public class MainClass {
  public static void main(String[] args) {
    //Create new BuilderTrial instances
    BuilderTrial one = new BuilderTrial("Becker", 35);
    BuilderTrial two = new BuilderTrial("Becker", 35);
    BuilderTrial three = new BuilderTrial("Agassi", 33);
    //one and two hold the same data in different objects
    //three holds different data
    System.out.println("One>>>" + one);
    System.out.println("Two>>>" + two);
    System.out.println("Three>>>" + three);
    System.out.println("one equals two? " + one.equals(two));
    System.out.println("one equals three? " + one.equals(three));
    //As one and two hold the same data, the same hashcode is returned.
    System.out.println("One HashCode>>> " + one.hashCode());
    System.out.println("Two HashCode>>> " + two.hashCode());
    System.out.println("Three HashCode>>> " + three.hashCode());
  }
}
class BuilderTrial {
  private String name;
  private int age;
  public BuilderTrial(String name, int age) {
      this.name = name;
      this.age = age;
  }
  public static void main(String[] args) {
  }
  public boolean equals(Object objCompared) {
      if (!(objCompared instanceof BuilderTrial)) {
          return false;
      }
      BuilderTrial rhs = (BuilderTrial) objCompared;
      return new EqualsBuilder().append(name, rhs.name).append(age, rhs.age)
                                .isEquals();
  }
  public String toString() {
      return new ToStringBuilder(this, ToStringStyle.MULTI_LINE_STYLE).append("Name",
          name).append("Age", age).toString();
  }
  public int hashCode() {
      return new HashCodeBuilder(15, 19).append(name).append(age).toHashCode();
  }
}

One>>>BuilderTrial@a981ca[
  Name=Becker
  Age=35
]
Two>>>BuilderTrial@e7b241[
  Name=Becker
  Age=35
]
Three>>>BuilderTrial@167d940[
  Name=Agassi
  Age=33
]
one equals two? true
one equals three? false
One HashCode>>> -923455822
Two HashCode>>> -923455822
Three HashCode>>> -1433293806